It’s hard to win in baseball if you don’t score runs. And this season, the Red Sox aren’t scoring. They’re on pace to score about 28 percent fewer runs than last season.

If they want to turn things around, the most important thing the Red Sox can do is boost their slugging percentage, which has fallen from a league-leading .446 in 2013 to a near-bottom .369. That’s not an opinion or a coaching tip. It’s what the numbers tell us.

Are you sure it’s not a lack of clutch hitting?

Important as it is for teams to hit well with runners in scoring position, it’s just as important for them to get lots of runners in scoring position in the first place.

Last year’s Red Sox, for instance, were a much better clutch-hitting team. They hit .278 with runners in scoring position, and each at-bat with runners in scoring positions translated into .43 runs. This year’s team is hitting .230 and averaging .36 runs per at-bat.

But last year’s team also had many more opportunities to hit with runners in scoring position, 1559 in total. This year’s team is on pace for just 1320 such opportunities. That means that even if they were just as good a clutch-hitting team, they’d still score 14 percent fewer runs.

So what does lead to run scoring?

The surest way to score runs is to get lots of players on base and then slug them home. OPS, which measures precisely those two things, turns out to be a remarkably good predictor of runs. Virtually all high-OPS teams are high-scoring teams, and vice versa. The chart below shows how tight this relationship really is.

Does OPS help explain this Red Sox season?

Defensively, the Red Sox have been playing fairly well. They’ve given up slightly more runs per game than last year, but not many.

Offense is a different story. On their way to the 2013 World Series championship, the Red Sox OPS was an MLB-leading .795. This year, it has dropped to .685. And it’s not as if league-wide pitching has gotten better and everyone’s OPS has collapsed. The league-wide average has fallen just 8 points.

The big reason for the falloff in OPS is that the Red Sox have the fourth-worst slugging percentage in baseball. Partly this is because the Red Sox just aren’t getting enough hits, and partly it’s because too few of their hits go for extra bases.

Multi-base hits of all types are way down from last year. Doubles have fallen more than 20 percent, triples 30 percent, and home runs 32 percent. And yet, even if the Red Sox were hitting the same proportion of multi-base hits as last year, their slugging percentage would be .393, which is just about average.

By contrast, if they had the same number of hits as last year, along with this year’s falloff of multi-base hits, they’d be slugging .419.

Is it the whole team, or just some players?

The Red Sox have obviously lost some key players, like Jarrod Saltalamacchia and Jacoby Ellsbury, both of whom were strong run-generators. And certainly Stephen Drew’s long absence from the lineup hasn’t helped.

But even the returning players are faring worse this year than last. Mike Napoli’s slugging percentage has dropped 9 percent, David Ortiz’s is down 12 percent, and Jonny Gomes’s is off 17 percent. There isn’t a single player whose 2014 slugging percentage is higher than 2013.

SLG 2013

SLG 2014

Non-returning

Jarrod Saltalamacchia

.466

-

Jacoby Ellsbury

.426

-

Jose Iglesias

.409

-

Returning

Mike Napoli

.482

.441

Dustin Pedroia

.415

.387

Stephen Drew

.443

.256

Will Middlebrooks

.425

.324

Jonny Gomes

.426

.354

Shane Victorino

.451

.352

David Ortiz

.564

.494

Daniel Nava

.445

.299

Mike Carp

.523

.286

New

A.J. Pierzynski

-

.348

Xander Bogaerts

-

.362

Brock Holt

-

.433

Jackie Bradley

-

.310

Grady Sizemore

-

.324

Source: Baseball-Reference.com, through 88 games

What is more, Ortiz, Pedroia, and Gomes are not only underperforming relative to last year, they’re underperforming relative to their career averages, which suggests that this isn’t just about players who had a great 2013 and who are coming back to earth.

One possibility would be that the influx of new and slumping players in the lineup has made it easier for pitchers to work around the more fearsome hitters. But it could also be that Ortiz and Gomes have lost a step, or perhaps nothing more than a run of collective bad luck.

Is there any hope for the rest of the season?

Probably not. The good news is that there’s a lot of room for improvement in the Red Sox lineup. If some of the key players from last year started hitting for power again, the Sox would be scoring more runs and winning more games. But even if the Sox play as well in the second half of this season as they did in the latter half of last year, they’d still end up with a record around .500, which is almost certainly not enough to get them into the playoffs.

Evan Horowitz digs through data to find information that illuminates the policy issues facing Massachusetts and the U.S. He can be reached at evan.horowitz@globe.com. Follow him on Twitter @GlobeHorowitz

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